Reprinted from 
BULLETIN OF MARINE SCIENCE 
OF THE GULF AND CARIBBEAN 
Vol.  13, No. 2, pp. 267-281 
JUNE, 1963 
A CONTRIBUTION TO THE BIOLOGY OF 
H. B. MOORE, THELMA JUTARE, J. A. JONES, B. F. McPHERSON 
AND C. F. E. ROPER 
Institute of Marine Science, University of Miami 
ABSTRACT 
The biology of Tripneustes has been studied for several years in Miami 
and Bermuda. It spawns in the spring and summer but with a very different 
spawning pattern in different years. First spawning seems to be triggered 
by temperature, and successive spawnings by attainment of a gonad size 
which increases during the season. Winter growth of the gonad and its rate 
of build up between spawnings is negatively correlated with temperature, 
as is test growth. Herrnaphroditism was common in a year group which 
was in the immature stage during an unusually cold winter. A tentative 
estimate has been made of food intake and of the efficiency of its conver- 
sion into urchin tissue. 
INTRODUCTION 
Commencing in 1937, a few observations on Tripneustes esculentits 
(Leske) were made by one of us (H.B.M.) in Bermuda. In 1959, 
McPherson and, in I960, Roper made the species the subject of a special 
study in a course in marine ecology at the University of Miami. In 1961, 
Jones carried out, in the same course, a series of field experiments. In 
1960-61, a grant from the National Science Foundation (G-14967) allowed 
the senior author and Thelma Jutare to bring together the existing data 
and amplify them, particularly by extending the series of observations on 
gonad changes and growth. This study was curried out along with one on 
the urchin, Lytechinus variegatus (Moore, et ?/., 1963), and affords a 
comparison of the biology o!' the two species. Of the two. Tripneustes is 
the more tropical in its distribution. It does not extend as far north as 
Lytechinus on either the Atlantic or Gulf of Mexico coasts and is probably 
not abundant north  of south Florida. 
Lewis (1958) has made a valuable study of Tripneustes in Barbados, 
in which he describes their growth, gonad changes, and planktonic history, 
together with notes on their general biology. 
We wish to thank the National Science Foundation for their support of 
these studies, as well as many members of the University of Miami 
Marine Laboratory who have helped from time to time. 
DISTRIBUTION 
Tripneustes does not extend quite so Irish into the intertidal region as 
does Lytechinus, rarely being exposed at low water.  It may, however, 
occur in intertidal pools in Bermuda, and in Bimini young individuals 
l Contribution   No.   472   from   The    Marine   Laboratory,    Institute   of   Marine   Science, 
University  of  Miami. 
268 Bulletin of Marine Science of the Gulj and Caribbean        17-3(2) 
have been seen in pools in a heavily splashed area above high water mark 
but no adults were seen there. At Sewage Beach, on Virginia Key, Miami, 
where most of the recent collecting was done, "grass" flats extend out 
from the lower intertidal zone for about a kilometer, and the heavy grass 
cover gives place to open sand at a depth of about a meter at extreme 
low water. Lytechinus is abundant over the entire extent of the grass flats, 
but Tripneustes is much less abundant and mainly confined to the outer 
edge. Tripneustes also showed some seasonal movement. Lytechinus tends 
to mask itself with pieces of shell at all times. Tripneustes, during the 
winter, was frequently found in open patches among the grass and 
without masking. During the spring, as the light became stronger, they 
were seen to mask themselves, but usually with pieces of alga rather 
than shell and, as summer advanced, they tended to move from the 
open areas into the cover of dense grass. When kept in indoor tanks, 
both species showed only small tendency to mask if conditions were rather 
dark, but they masked with anything available and moved into shaded 
areas when sunlight was admitted. Lewis states that, in Barbados, 
Tripneustes tends to aggregate on and under rocks in March and April 
and has dispersed into the open again by August. He associates this 
aggregation with spawning, which occurs in that period. He also states that 
the older individuals tend to move offshore for part of the year. 
BREEDING 
Tripneustes was not common in Bermuda, so only small samples could 
be examined. At Miami, fifty urchins were examined each time. Test 
diameter was taken as a standard measure of size, but a calibration curve 
was established relating diameter to test volume by displacement, this value 
including spines. A smear of the gonad was examined to determine sex and 
condition, and the gonads then removed and their volume determined by 
10. Gonad Volume 
displacement.  Relative gonad size is expressed  as ? 
Test Volume 
This value is comparable with that previously used by the senior author 
(Moore, et al., 1963), but not with that of Lewis (1958). 
The Bermudian series was not sufficient to show more than an indication 
of autumn or winter spawning (Fig. 1). The three years of studies at 
Miami showed a strikingly different pattern of gonad changes. The fact that 
even minor fluctuations were closely parallel in males and females point 
to such fluctuations being significant and not due to inadequate sampling. 
10.  G.V. 
In   1959, gonad  volumes ?=r^?   were  small,  not  attaining  a  value 
of 0.7 until June, and with a maximum for the year of about 0.8. There 
were apparently four successive spawnings, and there must have been 
at least one more in the autumn-winter period when observations were 
1963] Moore, el. al.: Biology of Tripneustes 269 
JAN i FEB, MAR , APR , MAY . JUN . JUL , AUG , SEP , OCT , NOV .DEC 
FIGURE  1.   Seasonal changes in gonad volume expressed as 
in Tripneustes. 
10. Gonad Volume 
Test Volume 
270 Bulletin of Marine Science oj the Gulj and Caribbean        [13(2) 
discontinued. In 1960, the build up of the gonads took place earlier, 
reaching a value of 0.7 in March, and with a maximum of about 0.9. 
However, spawning ceased earlier than in the previous year, the last 
cycle commencing in June. In 1961, the first spawning was in February, 
compared with March the previous year, and at its commencement the 
gonads had already reached a value of over 0.9. This spawning was 
prolonged and heavy. There was then a long build up period, the gonads 
reaching a value of over 1.1 in July and then commencing a second 
prolonged and heavy  spawning. 
In many animals, the initiation of spawning has been shown to occur 
when rising spring temperatures attain a certain value. With samples 
taken only every two to four weeks, in a period when the temperature may 
rise several degrees a month, we cannot define the exact temperature at 
which spawning commenced; but the values of 23.5?, 21.4?, and 
21.9?C in 1959, 1960, and 1961 are consistent with a critical temperature 
of about 22?C at which spawning commences but below which it will 
not occur. At the commencement of the first spawning of the year, gonad 
CD 
Q. 
CO 
t5 
1.0 A 
o 
o 
LU 
O 
o 
CD 
-2.0 
? 3 Months 
 6 Months 
-i.o 0 +1.0 +2.0 
DEVIATION ?C FROM I2yr. MEAN TEMP 
FIGURE 2. The relation of the gonad volume of Tripneustes at the start of the 
first spawning of the season (?~~?-) to deviation of the sea temperature 
in the previous three and six months from twelve-year mean values. 
1963] 
Q_ 
S 100 
CD 
co   75 
o 
Moore, et. al.: Biology of Tripneustes 111 
Q_ 
U_ 
O 
o 
CO 
<t 
CD 
50- 
25 
0 
0 .2 .6 .8 
2 
CO 
AMOUNT OF PREVIOUS BUILD UP [os^] 
FIGURE 3.   The relation in Tripneustes of the extent of spawning (expressed as in  n\r 
per cent of the previous build up) to the extent of this build up, as 10. G.V. 
T.V. 
sizes were very different in the three years?0.54, 0.79, and 0.93 in the 
males, and 0.53, 0.72, and 0.96 in the females. It has been shown in 
Lytechinus (Moore et al., 1963), and will be shown later for Tripneustes, 
that there is a close correlation between test growth and temperature, 
but that, surprisingly, the growth is greatest at low temperatures. The 
average sea temperature deviations from a twelve-year mean in the three 
months preceding were + 1.8?, ?0.7?, and ? 1.4?C respectively in 1959, 
1960, and 1961; and for the six months preceding spawning the values 
were +1.3?, 0.0?, and ? 0.7?C. This suggests that, while spawning is 
triggered at a temperature of about 22?C and does not occur below this 
temperature, the size of the gonad at first spawning depends on the degree 
of cold during the preceding winter (Fig. 2). We do not have comparable 
observations of the relation between gonad growth and temperature in 
Lytechinus. 
The completeness of emptying of the gonad at spawning is a function 
272 Bulletin of Marine Science of the Gulf and Caribbean        [13(2) 
of the previous build up of the gonad (Fig. 3). The massive build up in 
1961 before the critical temperature was reached was followed by a 
spawning equal to 95-100 per cent of the build up. Smaller build ups in 
other years were followed by as little as 33 per cent spawning. Except 
for the end of the spawning season, each spawning is succeeded rather 
abruptly by a period of build up. The size of the gonad at which the 
successive spawnings commence increases as the season advances, possibly 
in relation to the increasing temperature. It may be suggested that spawning, 
after the first of the season, is initiated by attainment of a certain tension 
in the gonad, as in some asteroids (Greenfield, 1959), but that this critical 
tension increases during the season. 
The intervals between samples were too long to allow very precise 
definition of the duration of the periods of spawning and build up. 
However, if rate of build up is expressed as percentage per 30 days of the 
mean value during the build up period, there is a significant (<1 per 
cent) correlation with temperature (Fig. 4), the rate decreasing with 
increasing temperature. Thus, both winter build up and build up after the 
successive spawnings are greatest at low temperatures, as is test growth. 
TEST GROWTH 
Lewis (1958) has afforded excellent coverage of growth in Barbados 
from cage experiments and from size frequency analysis of populations. 
He found that Tripneustes reached a diameter of about 80-90 mm in the 
.40        1.42 1.44 1.46 1.48 
LOG  TEMPERATURE ?C 
50 
FIGURE 4.   The relation in Tripneustes between the rate of gonad build up and 
temperature, both on logarithmic scales. 
1963] Moore, et. al.: Biology of Tripneustes 273 
first year and probably had a life span of about two years. Unfortunately, 
we have not been able to find a population of small Tripneustes during the 
present work, despite extensive search. We did, however, find a population 
at Bimini in pools above high water. These pools were kept supplied by 
?I2I 
o m 
en 
UJ IC a. 16- 
LU 
CO 
or 
o 
8- 
6- 
o 
? 0 
o 
40 50 60 70 80 90 
TEST   DIAMETER mm 
FtGURE 5.   The relation of the growth rate of Tripneustes in tanks (expressed 
as percentage volume increase per 30 days) to size of urchin. 
274 Bulletin oj Marine Science oj the Gulj and Caribbean        [13(2) 
rather continuous wave action. The urchins had a mean diameter of 24.8 
mm on June 20, 1961. This size was reached in Barbados in October- 
November, and, if the breeding periods are at all similar, it would appear 
that the Bimini population must have grown very much more slowly, since 
urchins presumably of the same age would have reached a size of about 
75 mm in Barbados. 
o 30 
o 
DC 
LU 
o_ 
LU 
(/) 
<* 
LU 
CC 
o 
20 
10 
or* 
(/) 
O 
or 
o 0 
0  0 
40 50 60 70 80 90 
TEST DIAMETER mm 
FIGURE 6. The relation of the growth rate of Tripneustes in field pens (ex- 
pressed as percentage volume increase per 30 days) to size of urchin. 
1963] Moore, et. ai: Biology of Tripneustes 275 
For larger urchins we have a year of observations under tank conditions 
and several months under natural conditions in a cage on the grass flats. 
In Lytechinus (Moore et ai, 1963), it was found that tank growth was 
much less than that in cages. In Tripneustes, tank growth, on a linear 
basis, was about half that in the sea. As shown below, there is a marked 
effect of temperature on growth rate, and allowance can be made for this 
so as to compare growth rate with size at a constant temperature (Figs. 5, 
6). 
Growth, expressed as percentage increase in volume per 30 days, shows 
a rapid decrease with increasing size. At a test diameter above 60 mm, the 
CO 
>- 
o 
ro 
or 
ixi 
o_ 
LU 
CO 
?t 
LU 
DC o 
6- 
o 
> 
2- 
0- 
co 
o 
DC 
CD 
FIGURE 
4- 
20 22 24 26 28 30 
TEMPERATURES 
7.   The relation of the growth rate of Tripneustes (expressed as per- 
centage volume increase per 30 days) in tanks to temperature. 
276 Bulletin of Marine Science of the Gulf and Caribbean        17-3(2) 
temperature-corrected rate of increase was 1-4 per cent in the tanks 
and about 5 per cent in the sea. An attempt to obtain a comparable figure 
from the Barbados data, but without a temperature correction, gives about 
16 per cent, which is much higher than at Miami and is consistent with the 
suggested difference in growth rates of small individuals between Bimini 
and Barbados. 
GROWTH AND TEMPERATURE 
It was shown that there is a correlation between gonad growth and 
temperature, growth being most rapid at low temperatures. The same is 
true of the test, as it was shown to be in Lytechinus. Figures 7 and 8 show 
the growth expressed as percentage in volume per 30 days in relation to 
CO 
>= 
o 10 
8- 
co 
LU 
en 
o 
LU 
4- 
2- 
(/) 
o 
CD 
G 
G 
23 24 25 26 27 
TEMPERATURES 
28 
FIGURE 8.    The relation of the growth rate of Tripneustes (expressed as per- 
centage volume increase per 30 days) in field pens to temperature. 
1963] Moore, el. ai. Biology of Tripneustes 277 
UJ CO g >- 
ID <c 25- 0 
_J o 
O o 
> rO 
o UJ 20- 
0 CO 
< UJ 
CO 
z: <t 15 ? 0 *^             ? H- UJ 
^ or 
o o 
or z G 
e> 10- 
260 270 
TEMPERATURES 
28.0 
FIGURE 9. An approximation of the relation of growth rate of Tripneustes 
(expressed as percentage volume increase per 30 days) to temperature in 
Barbados, from Lewis's data. 
temperature in tank and pen experiments. The regressions of growth on 
temperature are ?0.53? and ? 0.88" respectively. Lewis, although he 
does not give actual temperatures, comments upon the slowing of growth 
in Barbados in the summer. A tentative analysis of his data, applying 
temperatures from Lewis, 1960, yields a regression of growth on tempera- 
ture of ?3.71? (Fig. 9), which is greater than the Miami values. 
However, this is in part clue to a correlation in his data between size and 
temperature, and between growth rate and size. 
In Lytechinus, it was possible to show the decrease in growth rate of 
the test at the size at which the gonads commenced to grow. Lewis states 
that individuals with a test diameter of 20-30 mm had full gonads 
containing ripe eggs and sperm. No urchins of this size were available at 
Miami, but the ones taken at Bimini showed only small gonads beginning 
to develop at test diameters of 38 and 40 mm, and only a trace of gonad 
below 30 mm. It is probable, then, that growth of the gonads occurs later 
in the northern populations. Judging from the smallest Miami individuals 
measured (Fig. 10), gonad development probably commences at a test 
diameter of about 50 mm. This graph was obtained by taking all the gonad 
10. G.V. 
volume  (?yy? )  data throughout the year and expressing them  as 
278 
UJ 
Bulletin of Marine Science of the Gulf and Caribbean        [13(2) 
__l 
o 
> 
120 
UJ 110 
O 
>? 100 
o 
> 
o 
<t 
o 
o 
90 
80- 
70-1 
50 60 70 80 90 
TEST DIAMETER mm 
FIGURE  10. The relation of the gonad volume of Tripneustes, expressed as 
10. G.V. 
?~r-Tj?, to test diameter. For explanation, see text. 
percentages of the mean value for the sample. They were then combined 
and grouped by test diameter. 
The successive spawnings shown in Figure 1 allow a minimal estimate 
of total spawn output, but do not take into account such spawning as 
may have been taking place during the periods of build up. The annual 
..     ..                                   ?                         10.G.V. 
output vanes considerably in successive years. Expressed as   ^y  
1963] Moore, et. al.: Biology of Tripneustes 279 
it was 1.24, 0.81, and 1.34 in 1959, 1960, and 1961 respectively. Although 
the gonads were not consistently larger throughout the years in either sex, 
the annual output was consistently larger in each year in the females. The 
mean for the three years was 1.07 for the males, and 1.20 for the females, 
and expressed as a percentage of the maximum gonad volume, the mean 
output was 114 per cent in the males and 126 per cent in the females. 
FOOD INTAKE 
Some preliminary feeding experiments were carried out in the tanks. 
Newly collected urchins were kept in the tank for two to four days in 
running water and provided with an ample supply of clean Thalassia 
whose wet weight was obtained at the start and finish of the test. Further 
measurements will be needed throughout the year and under better 
controlled conditions, but the results so far available allow at least a 
tentative estimate of food requirements. 
Number of Mean Net weight of 
urchins temperature ?C Thalassia per urchin 
per day gm 
January-March 7 21.4 1.36 
March-April 4 23.2 3.16 
June-July 10 29.8 4.33 
Since there was some variation in the size of urchins used, these data 
have been normalized to a standard test volume of 250 cc, assuming that 
food intake is proportional to test volume. Comparable results for 
Lytechinus, if scaled up to a 250-cc urchin, would give an annual mean 
feeding rate of 7.15 gm dry weight per urchin per day, which is considerably 
greater than in Tripneustes. Further, there was no evidence of a seasonal 
change in feeding rate in Lytechinus. An average of the Tripneustes values 
gives about 3.0 gm wet weight per day, which is equivalent to 0.6 gm dry 
weight. 
A Tripneustes with a test diameter of 80 mm would increase in volume 
about 80 per cent in a year. From determinations, after decalcification, of 
the dry weights of gonads and of other tissues, this growth would be 
equivalent to non-gonad tissue production of 1.90 gm, compared with a 
gonad output of 4.37 gm, or a total of 6.27 gm. The dry weight of 
Thalassia eaten by an urchin this size would be 166 gm per year, so its 
efficiency would be about 3.8 per cent. This is close to the value of 3.0 
per cent obtained for Lytechinus. The feeding rate measurements were 
made in tanks, and growth rates were only about half the field values in 
these tanks. On the other hand, in the feeding tests the animals were 
brought straight in from the shore and kept for only two or three days, 
so probably behaved more normally than those kept in the tanks for long 
280 Bulletin of Marine Science of the Gulf and Caribbean        [13(2) 
periods. Normal feeding rates might perhaps be faster, in which case the 
efficiency might be less than 3.8 per cent but probably not as low as half 
this value. 
HERMAPHRODITES 
Studies of the gonads of Tripneustes and Lytechinus in 1959 showed 
that a considerable number of hermaphrodites were present. This had 
never been observed before by us in Bermuda or Miami, or, in the case 
of Tripneustes, by Lewis in Barbados. Hermaphroditism is a very rare 
occurrence in echinoids in general (Harvey, 1956). More complete studies 
were made on Lytechinus, where it was shown that there was a progression 
from predominantly male hermaphrodites early in the year to predom- 
inantly female ones later. The occurrence of the hermaphrodites was 
associated with the unusually low water temperatures early in 1958 when 
the urchins were small and their gonads were just beginning to form. In 
Tripneustes it was noted that, at the end of February, as many as 27 per 
cent were hermaphrodites and that the majority of these were predomin- 
antly male. Normal procedure was to examine a smear from only one of 
the five gonad sectors. It was found in Lytechinus that the hermaphroditism 
was not always found in all five gonad sectors and that examination of a 
single sector would locate only 43 per cent of the hermaphrodites. Even 
this figure is too high, since the condition might be localized in a portion 
of the section not taken in the smear sample. It is safe, then, to say that 
more than half the population, and possibly almost all of it, was herma- 
phroditic. 
SUMARIO 
UNA CONTRIBUCION A LA BIOLOGIA DE  Tripneustes esculentus 
La biologia de Tripneustes ha sido estudiada durante varios afios en 
Miami y Bermuda. Desova en la primavera y el verano, pero con dife- 
rente tipo de desove en afios distintos. El primer desove parece estar ame- 
nazado por la temperatura y los sucesivos por el aumento de tamano de 
las gonadas, que crecen durante la estacion. El crecimiento de las gonadas 
en invierno y su proporcion de crecimiento entre puestas esta en relacion 
negativa con la temperatura, igual quo el crecimiento de la concha. El 
hermafroditismo fue comun en un grupo de un ano que se presento en 
estado no maduro durante un frio invierno poco corriente. Se ha intentado 
un estimado de alimento tornado y su eficiencia para convertirse en tejido 
del erizo. 
REFERENCES 
LEWIS, J. L. 
1960.   The fauna of rocky shores of Barbados, West Indies. Can. J. Zool., 
38: 391-435 
1963] Moore, et. al.: Biology of Tripneustes 281 
GREENFIELD, L. J. 
1959. Biochemical and environmental factors in the reproductive cycle of 
the sea star Pisaster ochraceus (Brandt). Unpublished doctorate 
thesis, Stanford Univ., 1-143. 
HARVEY, E. B. 
1956. The American Arbacia and other sea urchins. Princeton, Princeton 
Univ. Press, 1-298. 
MOORE, H. B., THELMA JUTARE, J. C. BAUER AND A. C. JONES 
1963. The biology of Lytechinus variegatus. Bull. Mar. Sci. Gulf & Carib., 
13   (1):   23-53.